|BBC Research and Development Report Number 1992-11|
R&D Report 1992-11 : A modular wideband sound absorber G.D. Plumb The absorption coefficients were measured of various depths of RW2 grade Rockwool laid directly on the floor of the ISO-Standard reverberation room at BBC Research Department. The Rockwool was very effective as a wideband sound absorber. A new absorber was designed and tested, having the dimensions of existing BBC type A modular absorbers and containing RW2 Rockwool...
Keywords: absorption; absorber; rockwool; infill; hardboard; plywood; modular; coefficient; absorbers; panel; low frequency; coefficient curve; absorption coefficient; modular absorbers; infill panel; absorption coefficients; laid directly; reverberation room; band centre; lower frequencies
|BBC Research and Development Report 1955-08 : The Robbins-Joseph (R-J) loudspeaker enclosure - D.E.L. Shorter, H.D. Harwood, R.J. Packer|
R&D Report 1955-08 : The Robbins-Joseph (R-J) loudspeaker enclosure. D.E.L. Shorter, H.D. Harwood, R.J. Packer Tests have been carried out on a small loudspeaker cabinet known as the "R-J enclosure" which has been claimed to give improved bass reproduction. A small increase in efficiency at low frequencies resulting from the particular form of construction adopted is accompanied by some reduction of response in other parts of the frequency range.
Keywords: enclosure; response; loudspeaker; frequency; vent; impedance; enclosures; cone; axial; frequencies; cone unit; axial frequency; low frequencies; experimental enclosure; loudspeaker enclosure; cone units; sound absorbent; internal vent
|BBC Research and Development Report Number 1994-12|
R&D Report 1994-12 : A wideband absorber for television studios. M.D.M. Baird The acoustic treatment in BBC television studios has taken various forms to date, all of which have been relatively expensive, some of which provide inadequate absorption. An investigation has been conducted into the possibilities of producing a new type of wideband absorber which, would be more economic, also taking installation time into account, than earlier designs...
Keywords: absorption; absorber; wideband; frequency; acoustic; mineral; bbc; zintec; weldmesh; absorbers; zintec sheet; television studios; low frequency; band centre; mineral wool; frequency absorption; high frequency; octave band; wideband absorber; modular absorbers
|BBC Research and Development Report Number 1983-10|
R&D Report 1983-10 : The design of the prototype LS5/9 studio monitoring loudspeaker. K.E. Randall, C.D. Mathers The prototype of a new medium-power studio monitor is described which is physically small enough to be accommodated in areas where a large high-power monitor would be inappropriate. The main design and performance features are as follows:- A vented cabinet having a volume of 28 litres (1 cubic foot)...
Keywords: loudspeaker; unit; frequency; sound; diaphragm; drive; bbc; profile; crossover; prototype; sound level; pressure level; drive unit; drive units; sound pressure; studio monitoring; frequency splitting; monitoring loudspeaker; sound quality; harmonic distortion
|BBC Research and Development Report Number 1973-06|
R&D Report 1973-06 : Equipment for the transfer of digital video signals to paper tape C.K.P Clarke A digital computer can be used to simulate processing methods for the bit-rate reduction of digital television. To assess such methods, television signals must be converted to a form compatible with computer data-handling systems. This report describes equipment for transferring monochrome pulse-code modulation signals derived from a slide scanner to punched paper tape...
Keywords: signals; picture; digital; counter; sampling; samples; punched; bbc; paper; transfer; slide scanner; picture elements; paper tape; digital video; colour signals; coded colour; elements wide; paper tapes; video signals; horizontal counter
|BBC Research and Development Report 1996-03 : MPEG video coding: A basic tutorial introduction - S.R. Ely|
R&D Report 1996-03 : MPEG video coding: A basic tutorial introduction S.R. Ely MPEG has been outstandingly successful in defining standards for video compression coding, serving a wide range of applications, bit-rates, qualities and services on a worldwide basis. The standards are based upon a flexible toolkit of techniques for bit-rate reduction. MPEG video coding uses a combination of motion-compensated interframe prediction (for reducing temporal redundancy) with Discrete Cosine Transform (DC...
Keywords: prediction; dct; coding; picture; macroblock; coded; quantisation; mpeg; frame; coder; video compression; motion vectors; interframe prediction; video coding; variable length; dct coefficient; development department; motion vector; mpeg video; lower layers
|BBC Research and Development Report 1954-19 : The effect of the ground constants, and of an earth system, on radiation from a vertical aerial - G.D. Monteath, G.H. Millard|
R&D Report 1954-19 : The effect of the ground constants, and of an earth system, on radiation from a vertical aerial. G.D. Monteath, G.H. Millard This report describes a theoretical investigation into earth systems for medium-wave transmitting stations. The change in the groundwave field strength for a given input current, resulting from the installation of an earth system, has been calculated by the compensation-theorem method...
Keywords: earth; aerial; groundwave; system; ground; field; vertical; impedance; conducting; radius; semicircular earth; conducting ground; earth system; surface impedance; groundwave field; field strength; radiation pattern; vertical radiation; earth systems; circular earth
|BBC Research and Development Report 1996-10 : Radio with Pictures - A new medium - R.H.Evans|
R&D Report 1996-10 : Radio with Pictures - A new medium R.H.Evans The advent of digital radio broadcasting provides the broadcaster with the opportunity to convey a variety of data types, to considerably enhance a basic audio service. Analogue FM broadcasts already benefit from a variety of features from the Radio Data System (RDS), but while RDS uses an additional carrier to convey this digital data, the emerging all-digital services such as Eureka DAB, Inmarsat IDDS and WorldSpace, have the po...
Keywords: rwp; audio; pictures; programme; news; data; inmarsat; picture; receiver; radio; television news; rwp service; rwp programme; inmarsat idds; news programme; file size; digital radio; picture channel; rwp production; news service
|BBC Research and Development Report 1996-14 : WTDM Pilot Installation. A report on the work of RACE Project 2001 - C.D. Mathers (editor)|
R&D Report 1996-14 : WTDM Pilot Installation. A report on the work of RACE Project 2001 C.D. Mathers (editor) The BBC has led two RACE-sponsored projects to develop the technology for a fibre-optic based video signal router. In the first project, R1036, prototype equipment was developed; a demonstration in 1992 showed that optical routeing was not only feasible, but could accommodate different signal formats such as serial digital 625-line and uncompressed EU-95 HDTV...
Keywords: optical; wavelength; wtdm; network; pilot; nrk; installation; routeing; demultiplexer; equipment; network control; optical switching; final report; test bed; pilot installation; optical receiver; wavelength demultiplexer; insertion loss; clock recovery; wtdm pilot
|BBC Research and Development Report Number 1988-14|
R&D Report 1988-14 : On the design of loudspeakers for broadcast monitoring. C.D. Mathers By designing its own monitoring loudspeakers for about the past forty years, the BBC has achieved a degree of continuity and consensus in a subject where there are almost as many opinions as there are designers. This report describes the approach that has evolved within the Corporation towards design and assessment, and indicates how calculation and objective measurement are supplemented by experience and s...
Keywords: loudspeaker; bbc; design; frequency; damping; coil; acoustic; unit; diaphragm; drive; relative damping; damping factor; voice coil; tonal quality; bass unit; department report; volume velocity; drive unit; drive units; broadcast monitoring
|BBC Research and Development Report 1954-01 : The service area of the temporary television transmitters at Truleigh Hill, Pontop Pike and Glencairn - G.I. Ross|
R&D Report 1954-01 : The service area of the temporary television transmitters at Truleigh Hill, Pontop Pike and Glencairn. G.I. Ross This report gives the results of a survey of the service areas of the temporary low power transmitters at Trueleigh Hill, Pontop Pike and Glencairn. Tests in the service area of the Glencairn transmitter revealed that echo effects (ghosts) are not serious and are readily eliminated...
Keywords: pontop; truleigh; strength; pike; temporary; transmitters; transmitter; field; field strength; glencairn; permanent transmitter; medium power; pontop pike; mast height; truleigh hill; power transmitters; service area; average field; town field
|BBC Research and Development Report 1959-15 : A 41.5 Mc/s transistor field strength monitoring receiver - D.E.L. Shorter, G.J. Phillips|
R&D Report 1959-15 : A 41.5 Mc/s transistor field strength monitoring receiver. D.E.L. Shorter, G.J. Phillips This report describes a simple field strength recording receiver designed for monitoring television sound transmissions at comparatively short distances from the transmitter. The main characteristics of the receiver are a good gain stability, small size and low power consumption. The receiver has been designed for use at 41.5 Mc/s but receivers of similar design will be built for the oth...
Keywords: receiver; gain; amplifier; transistor; input; output; audio; emitter; circuit; stage; gain stability; crystal controlled; field strength; strength monitoring; stage gain; monitoring receiver; audio amplifier; local oscillator
|BBC Research and Development Report 1954-23 : The Neumann microphone Type U47 - H.D. Harwood, R.J. Packer|
R&D Report 1954-23 : The Neumann microphone Type U47 H.D. Harwood, R.J. Packer A new directional electrostatic microphone, type U 47, produced by the firm of Neumann in Berlin, incorporates the capsule originally designed for the type M 49 microphone but uses a cheaper form of head amplifier. The U 47 microphone is designed to give either cardioid or omnidirectional polar response. Frequency characteristics, sensitivity and noise have been measured on a single specimen for both conditions...
Keywords: microphone; omnidirectional; cardioid; characteristics; condition; output; neumann; frequency; frequencies; condenser; microphone capsule; mains unit; frequency characteristics; vertical plane; omnidirectional condition; neumann microphone; cardioid condition; microphone type; axbt microphone
|BBC Research and Development Report 1960-03 : The power gain of multi-tiered VHF transmitters aerials - P. Knight, G.D. Monteath|
R&D Report 1960-03 : The power gain of multi-tiered VHF transmitters aerials P. Knight, G.D. Monteath Transmitting aerials for vhf broadcasting usually consist of a number of similar groups or tiers of radiating elements, spaced at intervals along a supporting mast. The power gain of such an arrangement depends on the number of tiers, on the spacing between them, and also on the vertical radiation pattern of each individual tier...
Keywords: ooooo; ooo; oooooo; mmmmm; oooo; cfl; iiiii; gain; ooooo ooooo; tfl; moooo ooooo; power radiated; ooooo ooo; relative mutual; oooooo ooooo; radiation pattern; mutual resistance; iiiii iiiii; ooooo oooo
|BBC Research and Development Report Number 1977-12|
R&D Report 1977-12 : LF and MF propagation: a study of sky-wave field-strength variation. P. Knight LF and MF sky-waves vary in strength during periods which may be as short as a minute or as long as 11 years; this range includes day-to-day, diurnal, seasonal and solar-cycle variations. A detailed study has been made of all that is known about LF and MF sky-wave field-strength variation and this has been supplemented by further analysis of measured data.
Keywords: variation; measurements; field; propagation; strengths; strength; seasonal; median; frequency; ccir; diurnal variation; path length; field strength; ccir report; field strengths; solar activity; strengths measured; seasonal variation; median field; sunspot number
|BBC Research and Development Report 1996-13 : PlanTx: The universal tool for digital and analogue transmitter planning - M.P.Shovelton|
R&D Report 1996-13 : PlanTx: The universal tool for digital and analogue transmitter planning M.P.Shovelton Terrestrial radio-frequency planning is undergoing a revolution. With the movement of broadcasters towards digital transmission, the RF planning book is being re-written. The design of digital transmitter networks demands new techniques and innovative new prediction tools in order to allow these networks to be accommodated within the already tightly-packed broadcast spectrum (that is, be i...
Keywords: transmitter; matrix; interference; digital; transmitters; plantx; analogue; terrain; bbc; transmission; digital television; terrain path; field strengths; matrix interrogation; field strength; receiving point; analogue transmitter; incoming interference; interference analysis; protected field
|BBC Research and Development Report 1954-40 : The Telefunken microphones Type Elam 200 and Elam 201 - W.I. Manson, D.E.L. Shorter, H.D. Harwood, J. Nash, R.J. Packer|
R&D Report 1954-40 : The Telefunken microphones Type Elam 200 and Elam 201. W.I. Manson, D.E.L. Shorter, H.D. Harwood, J. Nash, R.J. Packer Tests have been carried out on specimens of the Telefunken electrostatic microphones type ELAM 200 and ELAM 201. The ELAM 200 microphone is pressure-operated while the ELAM 201 can be switched to give either omnidirectional or cardioid characteristics; identical pre-amplifier arrangements are used for both types...
Keywords: elam; blam; microphones; sensitivity; microphone; omnidirectional; cardioid; frequency; transformer; impedance; noise level; magnetic fields; type elam; electrostatic microphones; frequency characteristics; output transformer; microphone type; sound level
|BBC Research and Development Report Number 1976-28|
R&D Report 1976-28 : Hadamard transformation: Assessment of bit-rate reduction methods. C.K.P. Clarke This report is concerned with the bit-rate reduction of signals produced by Walsh-Hadamard transformation of PCM television signals. The main characteristics of the transform signals are outlined and the methods of linear and non-linear coding used to reduce their bit rate are described. It was found that, with linear coding, a slightly higher bit rate is required to describe the transform coeff...
Keywords: transform; bits; coefficients; signal; coding; hadamard; errors; signals; impairment; sampling; subjective tests; coding system; colour bars; alphanumeric characters; bit rate; transform signals; signal energy; transform signal; test card; walsh functions
|BBC Research and Development Report 1996-12 : Mobile Broadband System. A report on the work of RACE Project 2067 - J.T. Zubrzycki|
R&D Report 1996-12 : Mobile Broadband System. A report on the work of RACE Project 2067. J.T. Zubrzycki Mobile Broadband System (MBS) is a wireless cellular radio network capable of carrying digital signals at bit rates sufficient for digital video, including compressed HDTV. The technological feasibility has been studied in RACE* Project 2067 MBS, which had the aim to extend the Broadband Integrated Services Digital Network (B-ISDN) to mobile users, providing much higher capacity to users than ...
Keywords: mbs; mobile; ghz; base; broadband; demonstrator; antennas; antenna; project; diversity; diversity switch; display mode; base station; mbs demonstrator; race project; urban street; broadband system; base stations; mobile broadband; demonstrator measurement
|BBC Research and Development Report Number 1994-14|
R&D Report 1994-14 : The sound insulations of studio doors: Part 1: Door Blanks G.D. Plumb, R. Clark The sound insulations of a range of different door blanks were measured. The results were compared with the sound insulations of existing BBC door blanks. The new doors were made from medium density fibreboard (MDF) which is more stable than the blockboard used in existing studio doors. Consequently, they should require less maintenance and adjustment and should have a longer lifespan...
Keywords: mdf; door; insulations; bitumen; damping; measured; bbc; sound; acoustic; lightweight; band centre; lightweight door; sound insulations; damping mat; measured sound; octave band; door blank; door blanks; bitumen damping; sound insulation
|BBC Research and Development Report 1954-07 : Modifications to the Brookmans Park Home-service mast-radiator - P. Knight, G.J. Phillips|
R&D Report 1954-07 : Modifications to the Brookmans Park Home-service mast-radiator. P. Knight, G.J. Phillips The report describes modifications to the London Home-Service mast-radiator completed in September 1952. Provision has been made for driving the mast simultaneously at the base and across the break previously used for series loading. New components have been installed in the A.T.H., both for base-funding (standby circuit) and for double-feeding (main circuit)...
Keywords: mast; current; base; minimum; transmission; impedance; aerial; radiation; circuit; power; field strength; standby circuit; current distribution; mast transmission; radiation pattern; sky wave; radiation patterns; brookmans park; department report; vertical radiation
|BBC Research and Development Report 1954-13 : The Klein-Plessey Ionophone loudspeaker - J.R. Chew|
R&D Report 1954-13 : The Klein-Plessey Ionophone loudspeaker. J.R. Chew A novel type of loudspeaker, known as an "Ionophone", has been tested. In this loudspeaker the conventional vibrating diaphragm is dispensed with and the sound is produced by a modulated r.f. corona discharge. The device is used in conjunction with a horn radiator and its main field of application is therefore in the high-frequency range; smooth response can be obtained up to at least 20 kc/s...
Keywords: frequency; ionophone; horn; distortion; output; tuning; loudspeaker; axial; corona; overload; quartz tube; overload point; axial frequency; frequency characteristics; tuning control; frequency characteristic; mains voltage; undistorted output; divider network
|BBC Research and Development Report Number 1966-28|
R&D Report 1966-28 : The design of a low-frequency unit for monitoring loudspeakers. H.D. Harwood The present state in the design of low-frequency loudspeaker units is reviewed and the areas where improvement is desired are indicated. Experimental details are given leading to the design of 12 in. (305 mm) unit incorporating a vacuum-formed cone of toughened polystyrene with a p.v.c. (poly-vinyl chloride) surround and it is shown by objective and by listening tests that this design is superior to...
Keywords: cone; frequency; surround; mould; unit; shape; characteristic; axial; goodmans; loudspeakers; listening tests; bextrene cone; frequency characteristic; flat region; axial frequency; monitoring loudspeakers; power handling; frequency range; voice coil; technological report
|BBC Research and Development Report Number 1984-12|
R&D Report 1984-12 : The susceptibility of aeronautical navigational aids to interference from adjacent-band broadcast transmissions. G.H. Millard Measurements to determine the susceptibility of some airborne navigation receivers to interference from v.h.f/f.m sound transmissions are described. The measurements were designed to investigate both the response to interference radiated in-band and to intermodulation in the receivers ...
Keywords: receiver; ils; interference; intermodulation; frequency; signal; mhz; broadcast; transmissions; khz; field strength; receiver intermodulation; broadcast transmissions; sound broadcasting; wanted signal; intermodulation products; interfering signals; protection ratio; ils receiver; intermodulation product
|BBC Research and Development Report Number 1986-13|
R&D Report 1986-13 : VHF-FM radio broadcasting: tests to compare horizontal, vertical and mixed polarisations. G.H. Taylor, D.S. Cox The BBC is re-engineering its VHF-FM radio networks from horizontal to mixed polarization. This Report describes tests carried out to monitor this change and which confirm the advantages of mixed polarization. Tests from the BBC transmitting station at Wenvoe to compare vertical and horizontal polarization are described...
Keywords: antenna; multipath; polarized; receiving; wrotham; signal; antennas; polarization; reception; horizontal; received signal; polar diagrams; receiving antenna; wing mounted; horizontally polarized; multipath interference; signal strength; mixed polarized; polarized receiving; vertically polarized
|BBC Research and Development Report Number 1966-39|
R&D Report 1966-39 : Mutual resistance between radiating elements mounted on cylinders: application to vhf aerial gain calculation P. Knight, R.E. Davies A method for calculating the gain of a v.h.f. aerial from the mutual resistances between the radiating elements is described. The computation of mutual resistances between dipoles and unipoles mounted on a support mast is discussed. A set of tables of mutual resistances is included, together with notes on their use.
Keywords: dipole; dipoles; gain; relative; radiating; tangential; radiated; mutual; doublets; cylinder; free space; mutual resistances; mutual resistance; tangential doublets; radiating elements; total power; radiation pattern; relative mutual; power radiated; vertical dipoles
|BBC Research and Development Report Number 1970-31|
R&D Report 1970-31 : VHF receiving aerials: The use of active elements D.J. Whythe An array of half-wavelength dipoles forms the most convenient type of aerial for VHF television re-broadcast reception. The principles are well-known by which such an array can be designed to have any specified directivity but re-radiation from the dipole makes it difficult to implement those principles in practice. This report shows that the difficulty can be overcome by incorporating an amplifier directly across...
Keywords: dipole; array; dipoles; directivity; input; active; impedance; amplifier; rth; terminals; mutual impedances; field strength; input conductance; amplifier input; input impedance; active receiving; basic pattern; noise factor; active dipole; department report
|BBC Research and Development Report Number 1976-29|
R&D Report 1976-29 : The design of the miniature monitoring loudspeaker Type LS3/5A. H.D. Harwood, M.E. Whatton, R.W. Mills This report describes the design of a miniature two-unit loudspeaker of adequate sound quality and loudness to serve as a monitor in conditions where larger existing designs would be unusable. Details are given of the construction and performance of the loudspeaker which is shown to be equally suitable for monophonic, stereophonic and quadraphonic purposes.
Keywords: loudspeaker; sound; impedance; bbc; unit; cabinet; axial; frequency; resonance; design; report describes; loudspeaker type; sound level; sound quality; monitoring loudspeaker; resonance frequency; stereo performance; miniature monitoring; british broadcasting
|BBC Research and Development Report Number 1978-21|
R&D Report 1978-21 : Narrow-band FM system for television links: interference between fm and am television signals. N.H.C. Gilchrist, A.G. Lyner The Band-V fm television links used for television outside broadcasts have suffered more and more from interference as the network of uhf television broadcasting transmitters has expanded. There is also thought to be an increasing danger that Band-V links will cause interference to broadcast television reception...
Keywords: mhz; signal; interference; interfering; channel; television; sidebands; signals; frequency; system; sidebands retained; protection ratios; carrier rest; rest frequency; sound channel; sound subcarrier; experimental arrangement; upper sidebands; television signals; lower sidebands
|BBC Research and Development Report Number 1990-15|
R&D Report 1990-15 : The design and application of modular, acoustic diffusing elements. R. Walker The requirements for and the advantages of a modular acoustic diffusing element are described. This module was intended to complement the existing range of acoustic absorbing elements already in widespread use. The theoretical background to the principles is summarised, based on the published work of M.R...
Keywords: acoustic; diffusers; bbc; primitive; frequency; modular; diffusing; sequence; module; diffuser; acoustic treatment; sound energy; primitive root; upper frequency; field trials; quadratic residue; frequency limit; acoustic diffusing; diffusing elements; incident sound
|BBC Research and Development Report 1956-17 : The design of the PGD and PGS Ribbon microphones final report - H.D. Harwood, D.E.L. Shorter|
R&D Report 1956-17 : The design of the PGD and PGS Ribbon microphones final report H.D. Harwood, D.E.L. Shorter This report completes the account begun in Report M-015, of the design and performance of the new ribbon type pressure-gradient microphones. Additional information on performance, including measurements of wind noise and non-linearity, is given.
Keywords: ribbon; microphone; pgs; response; microphones; frequencies; impedance; frequency; transverse; resonance; pgs microphones; noise output; frequency response; ribbon microphones; microphone type; transverse resonance; final report; wind noise; pgs microphone; motional impedance
|BBC Research and Development Report 1956-01 : The Philips moving-coil microphone Type EL.6040. - W.I. Manson|
R&D Report 1956-01 : The Philips moving-coil microphone Type EL.6040. W.I. Manson Laboratory tests have been carried out on two specimens of the Philips microphone type EL.6040. Measurements of frequency response, sensitivity, impedance and interference from magnetic fields have been made. The microphone has also been tested in the parabolic reflector PRB/2.
Keywords: microphone; frequency; ohms; response; ohm; impedance; specimen; output; parabolic; philips; response curve; centre pin; frequency response; tap set; parabolic reflector; small irregularities; microphone type; ohm output; axial frequency
|BBC Research and Development Report 1954-34 : A new photo-electric optical bench - W.N. Sproson|
R&D Report 1954-34 : A new photo-electric optical bench. W.N. Sproson An outline of the photoelectric method of testing lenses is given, together with some details of the two types of test pattern now in use and the form of aperture correction necessitated by the finite width of the scanning slit. The photoelectric test bench is described and a few preliminary results are quoted.
Keywords: lens; modulation; wave; test; bench; microscope; optical; pattern; slit; photoelectric; wave response; test object; square wave; optical bench; test pattern; wave grating; photoelectric optical; pattern frequency; sine wave; square waves
|BBC Research and Development Report 1996-11 : Motion estimation for MPEG-2 coding using 'true' vectors - G.A.Thomas|
R&D Report 1996-11 : Motion estimation for MPEG-2 coding using 'true' vectors G.A.Thomas The motion estimator is a key component of any MPEG-2 video coder. It is common practice to use a method based on block-matching, which generates vectors designed to yield good predictions of images to be coded, without regard for whether the vectors correspond to actual motion. This Report describes a method of deriving motion vectors for an MPEG-2 coder from a motion estimator designed to produce âtrueâ ...
Keywords: vectors; vector; refinement; field; coding; traced; pixel; tracing; sequences; motion; vectors derived; phase correlation; traced vectors; search range; motion estimator; motion estimation; vector field; test sequences; vector tracing; motion vectors
|BBC Research and Development Report Number 1990-01|
R&D Report 1990-01: Antennas for portable VHF-FM receivers. R.D.C. Thoday This report describes a number of compact antennas which have been considered as replacements for the standard whip antenna which is normally fitted to VHF portable receivers. A comparison made of their characteristics shows that, of the antennas considered in the survey, the quarter whip still provides the best sensitivity. However the normal-mode helix is a more convenient and compact antenna and is shown to perform bett...
Keywords: antenna; receiver; helix; whip; sensitivity; tuning; ferrite; antennas; impedance; portable; antennas considered; receiver cabinet; short whip; receiver input; whip antenna; ferrite antenna; input impedance; portable receiver; helix antenna; portable receivers
|BBC Research and Development Report 1959-08 : Low-signal amplifying valves for use at U.H.F. - R.G. Manton|
R&D Report 1959-08 : Low-signal amplifying valves for use at U.H.F. R.G. Manton The object of this report is to review some of the types of valve that are suitable for use in u.h.f. amplifying stages in receivers, and to describe units which have been constructed to test the performance of two of these valves at a frequency of about 655 Mc/s.
Keywords: amplifier; valve; output; input; amplifiers; anode; bandwidth; grid; gain; impedance; electrical circuit; input impedance; valve holder; output circuits; noise factor; mechanical layout; amplifying valves; positive feedback; output impedance; backwards attenuation
|BBC Research and Development Report 1955-05 : The artificial reverberation test set - A.E. Axon, C. Henocq|
R&D Report 1955-05 : The artificial reverberation test set. A.E. Axon, C. Henocq. This report looks at the Artificial Reverberation Test Set which contiunes previous work done by the department.
Keywords: reverberation; test; decay; set; machine; logarithmic; cathode; artificial; tone; calibration; jack marked; decay calibrator; test set; ray tube; artificial reverberation; time base; reverberation time; cathode ray; reverberation machine; tone source
|BBC Research and Development Report 1996-08 : The COFDM Modulation system: The heart of Digital Audio Broadcasting. - P. Shelswell|
R&D Report 1996-08 : The COFDM Modulation system: The heart of Digital Audio Broadcasting. P. Shelswell Digital audio broadcasting offers the potential to give every radio in Europe the sound quality of a compact disc. To accomplish this, it requires a rugged method of transmission. The coded orthogonal frequency division multiplexing (COFDM) modulation system was developed to meet this need. This Report describes the reasons why a new modulation process was needed, and explains how the COFDM sy...
Keywords: symbol; cofdm; signal; frequency; bbc; modulation; carriers; digital; dab; fourier; modulation system; correlation bandwidth; digital audio; audio broadcasting; guard interval; dab system; fast fourier; fourier transform; symbol period; time domain
|BBC Research and Development Report Number 1991-11|
R&D Report 1991-11 : Field strength prediction for VHF/UHF terrestrial broadcasting and mobile radio services R.S. Sandell, R.W. Lee, C.P. Bell The propagation curves used internationally for the planning of services in the VHF and UHF Broadcast Bands are those of CCIR Recommendation 370 and associated Report 239. Derivations from these are also used for Mobile Radio planning in this frequency range...
Keywords: terrain; ccir; prediction; curves; propagation; antenna; height; measurements; receiving; bbc; antenna height; data base; field strength; propagation curves; receiving antenna; height gain; mobile radio; standard deviation; terrain data; prediction method
|BBC Research and Development Report Number 1964-23|
R&D Report 1964-23 : Low noise amplifiers for UHF reception R.V. Harvey, J.B. Izatt, P.C.J. Hill Noise in broadcast receivers generally increase as the frequency increases, whereas noise from external sources decreases. In receivers designed for u.h.f. using conventional valve or transistor circuits, the noise is about 10 dB greater than the aerial noise. There is therefore an obvious economic advantage to be gained by reducing receiver noise at u.h.f., particularly for special purposes such as ...
Keywords: amplifier; frequency; noise; diode; idler; circuit; parametric; signal; pump; gain; negative resistance; electron beam; parametric amplifier; noise factor; tunnel diode; pump power; pump frequency; noise figure; signal frequency; pump oscillator
|BBC Research and Development Report Number 1960-07|
R&D Report 1960-07 : 'T'-type coaxial notch filters for use at VHF W. Wharton, R.E. Davies This report describes the theory of the "T"-type coaxial notch filter and presents design curves enabling the dimensions of practical filters to be calculated rapidly. the type of filter considered was first described by Sosin and provides a two-terminal impedance with a pole and zero close together in frequency...
Keywords: filter; frequency; notch; coaxial; equations; design; filters; pass; pole; admittance; vision carrier; required pole; notch filter; design curves; notch filters; coaxial elements; practical applications; pass frequency; coaxial notch; required pass
|BBC Research and Development Report Number 1977-30|
R&D Report 1977-30 : A wideband microstrip UHF hybrid. J.L. Riley The use of discrete power-splitting hybrids in uhf circuit design can cause unnecessary mismatches and losses at connector junctions. A printed hybrid, with similar electrical characteristics, overcomes these problems and offers further savings of space and cost. Tight coupling, however, is difficult to achieve in conventional microstrip construction...
Keywords: coupler; coupling; microstrip; impedance; lines; design; coupled; interdigitated; hybrid; directivity; microstrip transmission; indirect coupling; tight coupling; wideband microstrip; interdigitated coupler; overlay coupler; coupled lines; earth plane; characteristic impedance; direct coupling
|BBC Research and Development Report Number 1977-03|
R&D Report 1977-03 : Factors in the design of loudspeaker cabinets. H.D. Harwood, R. Matthews The mechanical properties of timber, wood products and other materials potentially suitable for the construction of loudspeaker cabinets have been measured and details of the results are given. Various commercially available damping materials have also been assessed and their relative efficiencies are listed...
Keywords: loudspeaker; damping; cabinet; materials; frequency; grain; material; modulus; elastic; resonance; loudspeaker unit; glass reinforced; elastic modulus; loudspeaker cabinets; damping material; sound pressure; panel damping; outer grain; relative response; reinforced plastic
|BBC Research and Development Report Number 1964-53|
R&D Report 1964-53 : Comparisons between three colour television cameras C.B.B. Wood Tests have been carried out to compare the performance of an experimental four-tube colour camera developed by E.M.I. Ltd, a three-tube plumbicon colour camera manufactured by Phillips and a three-tube image orthicon colour camera manufactured by Marconi, the output of each camera being, in each case, an NTSC coded signal...
Keywords: camera; orthicon; plumbicon; tube; subjective; cameras; image; colour; luminance; lipstick; fine detail; three colour; image orthicon; plumbicon camera; tube camera; three cameras; orthicon cameras; orthicon camera; colour television; subjective grade
|BBC Research and Development Report Number 1973-32|
R&D Report 1973-32 : Solid state sensors: The use of a single dimension 512 element array for film scanning D.T. Wright Following some early experiments with a 72 element self-scanned linear array of photo-diodes, a 512 element array was obtained. This has been used to scan continuously moving film since this provides a convenient means of assessing the potential of single dimension solid state image pick up devices...
Keywords: array; output; film; signal; mhz; scanning; scanned; clock; lens; saturation; stored correction; single dimension; clock pulse; array output; scanned picture; array box; incident light; field interval; background pattern; pulse breakthrough
|BBC Research and Development Report Number 1974-17|
R&D Report 1974-17 : The generation of video synchronising pulses and test waveforms by digital synthesis: Timing errors caused by quantising distortion P.A. Ratcliff Digital waveform-synthesis produces interval timing errors, or wave-shape distortion, when generation of transitions is required at intervals which are not integer multiples of the sampling clock period. A rule has been evolved to determine the timing accuracy with which a digital system, with quantisation limitations, is capable o...
Keywords: waveform; digital; pulse; synchronising; timing; analogue; pulses; sampling; jitter; waveforms; sampling clock; gradient rule; sample values; synchronising pulse; timing errors; video tape; digitally generated; clock period; synchronising pulses; digitally synthesised
|BBC Research and Development Report 1956-36 : The Service area of the Les Platons Television Transmitter - G.I. Ross, A.R. Williams|
R&D Report 1956-36 : The Service area of the Les Platons Television Transmitter G.I. Ross, A.R. Williams This report gives the results of field strength survey of the Les Platons television transmitter. The service provided in Jersey is very good. Guernsey, on the whole, has a good service, although a small area in the west of the island receivers a field strength of less than 100 uV/m. Ninety-seven per cent of the population of the Channel Isles is within the 0.1 mV/m field strength contour.
Keywords: les; platons; strength; guernsey; median; jersey; transmitter; field; field strength; channel; les platons; service area; television transmitter; receiving sites; channel isles; platons television
|BBC Research and Development Report Number 1973-13|
R&D Report 1973-13 : MF propagation: A wave-hop method for ionospheric field-strength prediction P. Knight A new method for calculating the strength of medium-frequency sky-wave signals at night is described. Estimated losses due to all the ionospheric and terrestrial factors which affect a wave as it propagates from transmitter to receiver are subtracted from the field strength which would arise if losses were absent...
Keywords: ionospheric; loss; field; paths; strength; reflection; polarisation; propagation; ground; magnetic; intermediate reflection; transmitting aerial; field strength; ground loss; field strengths; reflection loss; convergence gain; coupling loss; polarisation coupling; ground conductivity
|BBC Research and Development Report Number 1979-19|
R&D Report 1979-19 : Ground-wave propagation in a realistic terrain. J.H. Causebrook, B. Tait LF and MF ground-wave propagation over a realistic terrain has been found to be very different to that over an assumed smooth earth. This report describes the basic nature of these differences, which include a non-simple relationship for field variation with distance and a non-free-space relationship between magnetic and electric fields...
Keywords: field; khz; magnetic; electric; terrain; clutter; transmitter; measurements; bbc; impedance; free space; magnetic fields; electric field; realistic terrain; magnetic field; sketch map; park transmitter; surface impedance; perfectly conducting; smooth earth
|BBC Research and Development Report Number 1995-14|
R&D Report 1995-14 : Digital HDTV bit-rate reduction in the studio T. Vlachos, M.G. Croll Two novel source coding algorithms are presented which are suitable for the recording of digital High Definition Television signals. One of the bit-rate reduction schemes is based on the Wavelet Transform and the other on the Lapped Orthogonal Transform (LOT). According to the first scheme, a multi-layered, hierarchical description of the source signal is obtained by means of a quad-tree, half-band wavelet ...
Keywords: coding; wavelet; transform; quantiser; block; quantisation; digital; frequency; compression; entropy; reduction schemes; prediction template; higher frequency; digital hdtv; wavelet transform; wavelet filter; basis functions; arithmetic coding; lapped orthogonal; quantiser weights